The present invention relates to electromechanical transducers and more particularly relates to electromechanical transducers, which respond to electrical signals to produce mechanical vibrations at desired frequencies.
Electromechanical transducers can be employed as part of sonar devices, which are used to detect underwater objects. Such transducers may be either a projector or a receiver. A projector is a sonar transmitter which converts electrical signals to mechanical vibrations, while a receiver conversely intercepts acoustic vibrations and converts them into electrical signals. Projector and receiver arrays are formed from multiple projectors and receivers, which are then utilized typically in conjunction with a sea craft to detect underwater objects.
A projector comprises an electromechanical stack of ceramic elements that generate mechanical vibrations when an electrical signal is applied. Electrodes interposed between the ceramic elements are included for applying the electrical signal to the ceramic elements.
Many different types of sonar projectors are known. One type of projector is a flextensional transducer. In general, an electromechanical stack is housed within an elliptically shaped outer shell. Application of an electrical signal by the electrodes to the ceramic elements causes the electromechanical it stack to vibrate which, in turn, produces magnified vibrations of the outer shell. Thereafter, the vibrations generate acoustic waves in the water.
Another type of projector is commonly referred to as a slotted cylinder projector. The slotted cylinder projector includes a cylindrical actuator disposed inside an outer cylindrical shell. Both the cylindrical actuator and cylindrical outer shell include gaps that coincide in position with one another. When the cylindrical actuator receives an electrical signal(s), the cylindrical actuator and cylindrical outer shell vibrate at a desired frequency in a direction to decrease and increase the dimensions of the gap.
The cylindrical actuator of the slotted cylinder projector typically includes an electromechanical stack comprising ceramic elements interposed by electrodes. Present electromechanical stacks include ceramic elements with trapezoidal cross-sections and electrodes having rectangular cross-sections, so when interleaved together form the cylindrical shape of the typical slotted cylinder projector. The trapezoidal shape of the ceramic element is typically manufactured by machining a larger rectangular cross-sectioned ceramic plate. This added machining process makes trapezoidal ceramic elements and their respective electromechanical stacks expensive and time consuming to produce. Despite cost and significant time investment electromechanical stacks have been made in this manner for years. It can be appreciated that an inexpensive and timely-to-manufacture slotted cylinder projector is needed.
The present invention provides a slotted cylinder transducer assembly that addresses the problems mentioned previously. In one embodiment, the invention provides an improved slotted cylinder transducer assembly of the type, which has a cylindrical actuator having a gap and a cylindrical outer shell having a gap coinciding in position with the gap in the cylindrical actuator. The cylindrical actuator includes a plurality of ceramic elements and electrodes. The ceramic elements are disposed circumferentially and each of the electrodes are disposed adjacent to at least one of the ceramic elements. The improvement comprises the ceramic elements being shaped substantially in the form of a rectangular prism and the electrodes being shaped substantially in the form of a trapezoidal prism.
This invention provides a cylindrical actuator, which is easier and less expensive to manufacture. The electrodes used in the present invention are typically easier and cheaper to shape into the form of a trapezoidal prism than the previously mentioned ceramic plates.